Backpack



FIG. 1 is a front perspective view of the backpack;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a right elevation view thereof;

FIG. 5 is a left elevation view thereof; and,

FIG. 6 is a top plan view thereof.

The broken lines illustrate elements of the backpack which form no partof the claimed design.

CLAIM The ornamental design for a backpack, as shown and described.